Plastic Stopper

ABSTRACT

A stopper includes a main body portion defining an open rearward end configured to receive the plunger rod, an engagement portion provided along an inner circumference of the main body portion configured to engage at least a top portion of the plunger rod, a closed front end forming a flexible roof, and a first perimetrical skirt extending around an outer circumference of the main body portion toward the closed front end of the main body portion. When fluid pressure is increased inside the syringe barrel during an injection, the flexible roof expands in a radial direction toward an inner wall of the syringe barrel, the first perimetrical skirt is forced against the inner wall of the syringe barrel, and an engagement between the plunger rod and the engagement portion forces the main body portion to expand in the radial direction toward the inner wall of the syringe barrel.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/468,304 entitled “Plastic Stopper” filed Mar. 28,2011, which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates, in general, to a stopper assembly for use with asyringe and, more particularly, to a stopper assembly manufactured froma rigid or semi-rigid plastic material that provides an active sealingfunction.

2. Description of Related Art

Current syringe designs can typically be categorized as two-piecesyringes or three-piece syringes. A typical three-piece syringe includesa tubular barrel having an access opening formed at one end, and asmaller discharge opening formed at the opposing end. The lead end of anelongated plunger is received within the access opening of the barrel soas to be slidable within the barrel. Attached to the lead end of theplunger is a flexible sealing member or stopper that snugly sealsagainst the interior surface of the barrel. A needle, a threaded member,or a non-threaded member is usually attached to the discharge opening onthe barrel. The needle can be used to penetrate a surface while thethreaded member can be used to attach the syringe to another medicaldevice, such as a catheter. The flexible stopper is usually manufacturedfrom an elastomeric material, such as a rubber or a cross-linked orthermoplastic elastomer.

A two-piece syringe, on the other hand, includes a “stopper” that is inthe form of a rigid sealing disc, also known as a plunger rod head. Itis typically made of the same rigid plastic as the rest of plunger rod.The sealing force in a two-piece syringe comes from a thin elasticbarrel that deforms around the rigid plunger rod head.

During use, the discharge end of the syringe is initially placed incontact with a fluid. For example, the needle on the syringe can beinserted into a liquid medication. As the plunger is retracted withinthe barrel, a process known as aspiration, a negative pressure is formedwithin the end of the barrel so as to cause the fluid to be drawn intothe barrel. The syringe can then be moved to a second location whereadvancing the plunger within the barrel causes the fluid to be pushed orexpressed out the discharge end of the barrel.

Current two-piece and three-piece syringe designs suffer from variousdeficiencies. For instance, three-piece syringes that include anelastomeric or rubber stopper have a high passive contact pressurebetween the stopper and syringe barrel that is present during the shelflife and when the syringe is in use. This passive contact pressure canbe as high as approximately 300 psi or more. Accordingly, the syringebarrel requires relatively large barrel wall thickness in order toprevent localized barrel creep or bulging during the shelf life.Therefore, a need exists for a syringe that has a lower contact pressurebetween the stopper and the barrel such that localized bulging of thesyringe barrel is eliminated. Typical two-piece syringes also includesuch high passive contact pressures and suffer from similardeficiencies. Therefore, a need exists for a syringe manufactured usingless material to achieve thinner walls by addressing the bulging effectcaused by current stopper designs.

In addition, due to the high contact forces and high frictioncoefficient between current elastomeric or rubber stoppers and the innerwall of the barrels, current syringe designs must be lubricated with aliquid lubricant, such as silicone oil, so that break-loose andbreak-out hand forces required to operate the syringe are not too high.Accordingly, a need further exists for a plastic stopper that can beused with a syringe without silicone oil or other lubricants or thatallows for significantly lower hand forces when used with a lubricant.

Furthermore, current rubber stoppers are typically manufactured from aspecialized cross-linked rubber (e.g., polyisoprene) that requires aspecialized compression molding/curing process. Such a process cansignificantly increase the cost of manufacturing the syringe.Furthermore, significant waste materials are also produced during thecompression molding process. For example, in a typical manufacturingprocess, up to 30% of the rubber is discarded during manufacturing ofthe conventional elastomeric stopper. Accordingly, a need exists for astopper that can be efficiently manufactured, thereby reducing the costof manufacturing the syringe and reducing the waste materials producedduring the manufacturing of the syringe.

Conventional two-piece syringes also suffer from a variety ofdeficiencies. More particularly, conventional two-piece syringestypically include rigid plunger rod sealing edges. Such edges createvery high contact forces which increase the hand force necessary to movethe plunger. In addition, these high contact forces along the sealingedges significantly deform the barrel walls, which make two-piecesyringes incompatible with syringe pumps where the barrel bulge caninterfere with a pump clamping mechanism. Accordingly, a need exists fora syringe that has a lower contact pressure between the stopper and thebarrel such that localized bulging of the syringe barrel is eliminated.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a rigid plastic stopper thatallows for thinner syringe barrel walls relative to the rubber-basedconventional syringe stoppers. This is achieved because contact pressurebetween the rigid plastic stopper and the syringe barrel manufacturedfrom a similar material is much lower when the syringe is not in userelative to a conventional rubber stopper. This allows for theelimination of barrel creep or localized bulging issues. In addition,the thinner barrel wall provided by the lower contact pressure in thesyringe of the present invention also allows for lower material use andlower waste generation, thereby providing a “greener” syringe.

Furthermore, the lower contact pressure is achieved by providing theinventive rigid plastic stopper with an active sealing function suchthat when fluid pressure inside the syringe increases due to injection,sealing pressure between the stopper and the barrel also increases dueto three separate pressure activated actions. The first of these actionsis a flexing roof action in which a flexible roof of the stopper flexesinward and expands sideways in a radial direction. The next action is aflexing skirt action in which a perimetrical skirt extending around amain body portion of the stopper bends toward a wall of the syringebarrel. Finally, a sliding action is provided in which an engagementbetween the plunger rod and a notch formed in an interior portion of themain body portion of the stopper forces the main body portion to expandin the radial direction toward the inner wall of the syringe barrel. Inaddition, the present invention contemplates any of these three separatepressure activated actions, either individually or in combination, to beincorporated into a stopper.

A further object of the invention is to provide a plastic stopper thatcan be used with a syringe without silicone oil or other lubricants orthat allows for significantly lower hand forces when used with alubricant. The plastic stopper of the present invention is able toachieve these features due to a significantly lower coefficient offriction and contact area/pressure relative to a conventional rubberstopper. Another object of the invention is to provide a plastic stopperthat is manufactured of the same or similar resins for other injectionmolded syringe parts. This allows for a reduction in the cost relatingto material logistics and supply. Additionally, the plastic stopper ofthe invention is manufactured using significantly less material byweight relative to the conventional elastomers. The lower material usecan translate to lower cost and lower waste generation.

The particularly disclosed stopper design is manufactured from a rigidplastic material while also providing an active sealing function. Thestopper is adapted for attachment with a plunger rod for use within asyringe barrel.

According to one aspect of the invention, the stopper includes a mainbody portion defining an open rearward end configured to receive theplunger rod, an engagement portion provided along an inner circumferenceof the main body portion configured to engage at least a top portion ofthe plunger rod, a closed front end forming a flexible roof, and a firstperimetrical skirt extending around an outer circumference of the mainbody portion toward the closed front end of the main body portion. Whenfluid pressure is increased inside the syringe barrel during aninjection, the flexible roof expands in a radial direction toward aninner wall of the syringe barrel, the first perimetrical skirt is forcedagainst the inner wall of the syringe barrel, and an engagement betweenthe plunger rod and the engagement portion forces the main body portionto expand in the radial direction toward the inner wall of the syringebarrel, thereby providing a sealing pressure between the stopper and theinner wall of the syringe barrel. The stopper may further include asecond perimetrical skirt extending around an outer circumference of themain body portion toward the open rearward end of the main body suchthat the second perimetrical skirt provides stability to the stopper inan axial direction. When fluid pressure is decreased inside the syringebarrel during an aspiration, the second perimetrical skirt is forcedagainst the inner wall of the syringe barrel, thereby providing asealing pressure between the stopper and the inner wall of the syringebarrel.

The closed front end of the main body may have a conical shape with atip. The tip may include an extended portion configured to fit inside atip of the syringe barrel. In addition, an extension extending from thetip toward the open rearward end may be provided in connection with theplunger rod to cause the flexible roof to expand in the radial directiontoward the inner wall of the syringe barrel during an aspiration.

The engagement portion may be configured as a notch and the top portionof the plunger rod may include a tapered ring that engages the notch ofthe main body such that the engagement between the plunger rod and thenotch forces the main body portion to expand in the radial directiontoward the inner wall of the syringe barrel during both an injection andan aspiration. The notch may include an upwardly angled portion and adownwardly angled portion. The upwardly angled portion may have an angleof about 10° to about 80° as measured from a vertical line extendingbetween the upwardly angled portion and the downwardly angled portion,and desirably an angle of about 25° to about 55° as measured from avertical line extending between the upwardly angled portion and thedownwardly angled portion. The downwardly angled portion may have anangle of about 10° to about 80° as measured from a vertical lineextending between the upwardly angled portion and the downwardly angledportion, and desirably an angle of about 25° to about 55° as measuredfrom a vertical line extending between the upwardly angled portion andthe downwardly angled portion. Alternatively, the engagement portion mayinclude a protruding portion and the top portion of the plunger rod mayinclude a notch formed around an outer circumference thereof thatengages the protruding portion of the main body such that the engagementbetween the plunger rod and the protruding portion forces the main bodyportion to expand in the radial direction toward the inner wall of thesyringe barrel during both an injection and an aspiration.

The stopper, the plunger rod, and the syringe barrel may all bemanufactured from the same rigid or semi-rigid polymeric material. Therigid or semi-rigid polymeric material may have an elastic modulus inthe range of about 0.01 GPa to about 5 GPa, and desirably in the rangeof about 0.6 GPa to about 2 GPa. The rigid or semi-rigid polymericmaterial may be selected from the group consisting of: polyolefines,polyamides, polyesters, polystyrene, polyurethane, polycarbonate,acrylonitrile-butadiene-styrene, fluoropolymers, ionomers,polyacrylates, or any combination thereof.

The flexible roof may have a thickness of about 0.1 mm to about 3 mm,and desirably a thickness about 0.3 mm to about 1.2 mm. The firstperimetrical skirt may have a thickness of about 0.05 mm to about 3 mm,and desirably a thickness of about 0.2 mm to about 0.5 mm. The length ofthe first perimetrical skirt may be about 1 mm to about 10 mm. Thesecond perimetrical skirt may have a thickness of about 0.05 mm to about3 mm, and desirably a thickness of about 0.2 mm to about 0.5 mm. Thelength of the second perimetrical skirt may be about 1 mm to about 10mm.

According to another aspect of the invention, a syringe includes asubstantially cylindrical syringe barrel having a fluid dispensing endand an open end; a stopper configured to be received within the open endof the syringe barrel; and a plunger rod having a plunger rod bodyextending along a longitudinal axis. The stopper includes a main bodyportion defining an open rearward end configured to receive the plungerrod, an engagement portion provided along an inner circumference of themain body portion, a closed front end forming a flexible roof, and afirst perimetrical skirt extending around an outer circumference of themain body portion toward the closed front end of the main body. Theplunger rod body includes a front attachment end configured to engagethe engagement portion provided along the inner circumference of themain body portion of the stopper and a back end. When fluid pressure isincreased inside the syringe barrel during an injection, the flexibleroof expands in a radial direction toward an inner wall of the syringebarrel, the first perimetrical skirt is forced against the inner wall ofthe syringe barrel, and an engagement between the plunger rod and theengagement portion forces the main body portion to expand in the radialdirection toward the inner wall of the syringe barrel, thereby providinga sealing pressure between the stopper and the inner wall of the syringebarrel.

The front attachment end of the syringe plunger body may include anextension portion configured to contact a lower surface of the flexibleroof during an injection, thereby limiting the expansion of the flexibleroof in the radial direction.

According to yet another aspect of the invention, a plunger rod andstopper assembly adapted for use with a syringe barrel includes astopper and a plunger rod having a plunger rod body extending along alongitudinal axis. The stopper includes a main body portion defining anopen rearward end configured to receive the plunger rod, an engagementportion provided along an inner circumference of the main body portion,a closed front end forming a flexible roof, and a first perimetricalskirt extending around an outer circumference of the main body portiontoward the closed front end of the main body. The plunger rod includes afront attachment end configured to engage the engagement portionprovided along the inner circumference of the main body portion of thestopper and a back end. When fluid pressure is increased inside thesyringe barrel during an injection, the flexible roof expands in aradial direction toward an inner wall of the syringe barrel, the firstperimetrical skirt is forced against the inner wall of the syringebarrel, and an engagement between the plunger rod and the engagementportion forces the main body portion to expand in the radial directiontoward the inner wall of the syringe barrel, thereby providing a sealingpressure between the stopper and the inner wall of the syringe barrel.

These and other features and characteristics of the present invention,as well as the methods of operation and functions of the relatedelements of structures and the combination of parts and economies ofmanufacture, will become more apparent upon consideration of thefollowing description and the appended claims with reference to theaccompanying drawings, all of which form a part of this specification,wherein like reference numerals designate corresponding parts in thevarious figures. It is to be expressly understood, however, that thedrawings are for the purpose of illustration and description only andare not intended as a definition of the limits of the invention. As usedin the specification and the claims, the singular form of “a”, “an”, and“the” include plural referents unless the context clearly dictatesotherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a plunger rod, stopper, andsyringe barrel in accordance with an embodiment of the presentinvention;

FIG. 2 is a perspective view of a stopper according to a firstembodiment of the present invention;

FIG. 3 is a cross-sectional side view of the stopper of FIG. 2 takenalong line 3-3;

FIG. 4A is a cross-sectional side view of the stopper of FIG. 2 attachedto a plunger rod and positioned within a syringe barrel;

FIG. 4B is a cross-sectional side view of an alternative embodiment ofthe stopper of FIG. 2 having an alternative engagement mechanism betweenthe stopper and the plunger rod;

FIG. 5 is a side view of the plunger rod of FIG. 1;

FIG. 6A is a perspective view of the plunger rod of FIG. 1;

FIG. 6B is an alternative embodiment of the plunger rod of FIG. 6A;

FIG. 7 is a schematic view of the flexible roof of the stopper of FIG. 2in accordance with the present invention;

FIG. 8 is a perspective view of a stopper according to a secondembodiment of the present invention;

FIG. 9 is a cross-sectional side view of the stopper of FIG. 8 takenalong line 9-9;

FIG. 10 is a cross-sectional side view of the stopper of FIG. 8 attachedto a plunger rod and positioned within a syringe barrel;

FIG. 11 is a perspective view of a stopper according to a thirdembodiment of the present invention;

FIG. 12 is a cross-sectional side view of the stopper of FIG. 11 takenalong line 12-12;

FIG. 13 is a cross-sectional side view of the stopper of FIG. 11attached to a plunger rod and positioned within a syringe barrel;

FIG. 14 is a side view of a plunger rod for use with the stopper of FIG.11;

FIG. 15 is a perspective view of the plunger rod of FIG. 14;

FIG. 16 is a perspective view of a stopper according to a fourthembodiment of the present invention;

FIG. 17 is a cross-sectional side view of the stopper of FIG. 16 takenalong line 17-17;

FIG. 18 is a cross-sectional side view of the stopper of FIG. 16attached to a plunger rod and positioned within a syringe barrel;

FIG. 19 is a side view of a plunger rod for use with the stopper of FIG.16;

FIG. 20 is a perspective view of the plunger rod of FIG. 19;

FIG. 21 is a perspective view of a stopper according to a fifthembodiment of the present invention;

FIG. 22 is a cross-sectional side view of the stopper of FIG. 21 takenalong line 22-22;

FIG. 23 is a cross-sectional side view of the stopper of FIG. 21attached to a plunger rod and positioned within a syringe barrel;

FIG. 24 is a side view of a plunger rod for use with the stopper of FIG.21;

FIG. 25 is a perspective view of the plunger rod of FIG. 24;

FIG. 26 is a perspective view of a stopper according to a sixthembodiment of the present invention;

FIG. 27 is a cross-sectional side view of the stopper of FIG. 26 takenalong line 27-27;

FIG. 28 is a cross-sectional side view of the stopper of FIG. 26attached to a plunger rod and positioned within a syringe barrel;

FIG. 29 is a side view of a plunger rod for use with the stopper of FIG.26;

FIG. 30 is a perspective view of the plunger rod of FIG. 29;

FIG. 31 is a cross-sectional view of the stopper of FIG. 21 positionedat the end of a syringe barrel; and

FIG. 32 is a portion of FIG. 31 enlarged for magnification purposes.

DETAILED DESCRIPTION OF THE INVENTION

For purposes of the description hereinafter, the terms “upper”, “lower”,“right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, “lateral”,“longitudinal”, and derivatives thereof, shall relate to the inventionas it is oriented in the drawing figures. However, it is to beunderstood that the invention may assume various alternative variations,except where expressly specified to the contrary. It is also to beunderstood that the specific devices illustrated in the attacheddrawings, and described in the following specification, are simplyexemplary embodiments of the invention. Hence, specific dimensions andother physical characteristics related to the embodiments disclosedherein are not to be considered as limiting.

With reference to FIG. 1, a syringe, generally denoted as referencenumeral 10, includes a stopper 12 and a plunger rod 14. The stopper 12and plunger rod 14 are adapted for use within a syringe barrel 16. Thesyringe barrel 16 includes a distal or frontal end 18 which includes anoutlet opening and/or a mechanism for attachment of a separate medicaldevice (such as a catheter), shown in the form of a luer 20, and an openproximal or rearward end 22 for receiving the stopper 12 and plunger rod14 assembly. However, while the use of a luer type attachment isillustrated in FIG. 1, this is not to be construed as limiting thepresent invention as any suitable type of attachment for syringe 10 hasbeen contemplated. In addition, in certain syringe pump applicationswhere a low constant flow rate is required, an inner diameter of thesyringe type should have a maximum value of about 1.30 mm. The purposeof this small inner diameter is to increase pressure during a low flowrate infusion therapy. The increased pressure inside the syringe forcesthe flexible roof, described hereinafter, to expand in a radialdirection toward an inner wall of the syringe barrel and form a seal.For equal and constant flow rate, the small 1.30 mm syringe tip innerdiameter requires or creates a higher pressure than a standard syringetip inner diameter. While the figures herein depict a separate stopperand plunger assembly, it is contemplated that the stopper features maybe integrally formed with the plunger rod 14.

With reference to FIGS. 2 and 3, a first embodiment of the stopper 12includes a main body portion 24 defining an open rearward end 26configured to receive the plunger rod 14 and a closed front end 28 thatforms a flexible roof. The flexible roof has a thickness of about 0.1 mmto about 3 mm, and desirably a thickness of about 0.3 mm to about 1.2mm. The closed front end 28 of the main body portion 24 includes a firstangled portion 30 and a second angled portion 32, which are both part ofa single conical surface, that extend toward a tip 34, thereby providingthe closed front end 28 with a substantially conical appearance.However, this shape of the flexible roof is not to be considered aslimiting the present invention as the roof may be flat. Such a roofwould not provide flexing roof action in which a flexible roof of thestopper flexes inward and expands sideways in a radial direction.However, a stopper with a flat roof has been envisioned that includes aflexing skirt action in which a perimetrical skirt extending around amain body portion of the stopper bends toward a wall of the syringebarrel, and a sliding action that is provided in which an engagementbetween the plunger rod and a notch formed in an interior portion of themain body portion of the plunger forces the main body portion to expandin the radial direction toward the inner wall of the syringe barrel.

A first perimetrical skirt 36 is provided that extends around an outercircumference of the main body portion 24 toward the closed front end28. The primary purpose of the first perimetrical skirt 36 is to providean “active seal” between the stopper body and an inner wall 38 of thesyringe barrel 16 as will be discussed in greater detail hereinafter.The first perimetrical skirt 36 has a thickness from about 0.05 mm toabout 3 mm, and desirably a thickness of about 0.2 mm to about 0.5 mm.The length of the first perimetrical skirt 36 may be about 1 mm to about10 mm. In addition, the first perimetrical skirt 36 includes a tip thatcomes in contact with the inner diameter of the syringe barrel 16. Thetip may have any variety of localized shapes, such as, but not limitedto, round, angled, serrated, etc.

The first perimetrical skirt 36 may create a “dead space” of unusedmedication or other fluid at the end of an injection. To minimize this“dead space”, a protrusion (not shown) having a shape corresponding tothe “dead space” may be added to the inside of the barrel roof of thesyringe barrel 16. The protrusion is sized to correspond to the gapformed between the inside edge of the first perimetrical skirt 36 andthe main body portion 24. In addition, the protrusion may incorporate aninterruption or a plurality of interruptions.

The stopper 12 also includes a second perimetrical skirt 40 extendingaround an outer circumference of the main body portion 24 toward theopen rearward end 26. The primary purpose of the second perimetricalskirt 40 is to provide stability to the stopper 12 in an axial directionand to prevent tilting of the stopper 12. In addition, when fluidpressure is decreased inside the syringe barrel 16 during an aspiration,the second perimetrical skirt 40 is forced against the inner wall 38 ofthe syringe barrel 16, thereby providing a sealing pressure between thestopper 12 and the inner wall 38 of the syringe barrel 16. The secondperimetrical skirt 40 has a thickness from about 0.05 mm to about 3 mm,and desirably a thickness of about 0.2 mm to about 0.5 mm. The length ofthe second perimetrical skirt 40 may be about 1 mm to about 10 mm.

As shown in FIG. 3, the main body portion 24 of the stopper 12 issubstantially hollow and designed to receive an attachment portion 42 ofplunger rod 14. The main body portion 24 has a height, as measured fromthe bottom of the second perimetrical skirt 40 to the top of the firstperimetrical skirt 36 of about 2 mm to about 20 mm, and desirably about3 mm to about 8 mm. A notch 44 is provided that extends around an innercircumference of the main body portion 24. The notch 44 includes anupwardly angled portion 46 and a downwardly angled portion 48, therebyproviding the notch 44 with a conical cross-sectional shape. Theupwardly angled portion 46 has an angle of about 10° to about 80° asmeasured from a vertical line, and desirably has an angle of about 25°to 55°. The downwardly angled portion 48 has an angle of about 10° toabout 80° as measured from a vertical line, and desirably has an angleof about 25° to 55°. However, the shape of notch 44 is not to beconstrued as limiting the present invention as other interfaces betweenthe notch 44 and the attachment portion 42 of the plunger rod 14, suchas linear or curved interfaces, could be utilized to provide the samefunction. In addition, with reference to FIG. 4B, a notch 64 may beprovided at the end of the plunger rod 14 and the stopper 12 couldinclude a protruding portion 66 that engages the notch 64, therebyproviding the same function as the notch 44. While the shape of thenotch 64 is shown in the figures as having a substantially conicalcross-section, this shape is not to be construed as limiting the presentinvention as any suitable shape may be utilized.

The notch 44 is configured to engage with the attachment portion 42 ofthe plunger rod 14 such that, during an injection, the upwardly angledportion 46 engages the attachment portion 42, thereby forcing the mainbody portion 24 in a radial direction (i.e., toward barrel wall) suchthat a stronger seal is created between the main body portion 24 and theinner wall 38. During an aspiration, the downwardly angled portion 48engages the attachment portion 42, thereby forcing the main body portion24 in a radial direction (i.e., toward barrel wall) such that a strongerseal is created between the main body portion 24 and the inner wall 38.

The stopper 12 is desirably manufactured from a “rigid” or “semi-rigid”polymeric material with an elastic modulus in the range of about 0.01 toabout 5 GPa, and desirably in the range of about 0.6 to about 2 GPa. Thedesired Shore D hardness of the material is between about D30 and aboutD80. The stopper material may include, but is not limited topolyolefines (e.g., PE, PP, and their copolymers), polyamides (e.g.,nylons), polyesters (e.g., PET), polystyrene, polyurethane,polycarbonate, acrylonitrile-butadiene-styrene, fluoropolymers,ionomers, polyacrylates, or any other similar material. Moreover, anybio-derived, biodegradable, and recycled polymer with the elasticmodulus between about 0.01 and about 5 GPa may also be used with thestopper in accordance with the present invention. Since the stopper 12is manufactured from a “rigid” or “semi-rigid” polymeric material, asignificantly lower coefficient of friction and contact area/pressurerelative to a conventional rubber stopper is provided. Accordingly, thestopper 12 can be used with a syringe 10 without silicone oil or otherlubricants. In addition, the syringe barrel 16 may be made of the samematerial or a similar material as the stopper 12.

With reference to FIGS. 5 and 6A, the plunger rod 14 may include asyringe plunger body 50 having a front end 52 and a back end 54extending along a longitudinal axis X. The attachment portion 42 isassociated with the front end 52 of the syringe plunger body 50. Theattachment portion 42 includes a tapered ring 56 designed to engage thenotch 44 of the stopper 12. Alternatively, a pair of discrete ribs 57may be provided in place of tapered ring 56 (see FIG. 6B). The discreteribs 57 may be arranged in a cross-shape as shown in FIG. 6B such thatthe ends of the ribs engage the notch 44 at four discrete pointstherealong. However, this configuration is not to be construed aslimiting the present invention as any suitable number of discrete ribsmay be utilized or an interrupted tapered ring may also be used. Inaddition, instead of a continuous notch that extends around an innercircumference of the main stopper body, a plurality of discrete notches,corresponding to the number of discrete ribs, may also be utilized.

The front end 52 of the plunger rod 14 may also include an extensionportion 58 configured to contact a lower surface 60 of the flexible roofof the closed front end 28 during an injection only when or if maximumpressure reaches maximum design pressure, thereby limiting the expansionof the flexible roof in the radial direction to prevent the flexibleroof from collapsing if the syringe 10 is over-pressurized in an extremecase. The syringe plunger body 50 may also include a retaining ring 62positioned adjacent to the open rearward end 26 of the main body portion24 of the stopper 12. The retaining ring 62 is provided to prevent theplunger rod 14 from being removed from the syringe barrel 16. Withreference to FIG. 4A, when the plunger rod 14 is inserted into thestopper 12 through the open rearward end 26, the tapered ring 56 engagesthe notch 44 such that the plunger rod 14 is locked in place and isprevented from separating from the stopper 12.

The plunger rod 14 may be manufactured from the same material as thestopper 12. In addition, the plunger rod 14 and the stopper 12 may bemanufactured integrally to provide a two-piece syringe or separately toprovide a three-piece syringe.

With continued reference to FIG. 4A, the rigid plastic stopper 12includes an active sealing function such that when fluid pressure insidethe syringe 10 increases due to injection, as shown by the dashedarrows, sealing pressure between the stopper 12 and the syringe barrel16 also increases due to three separate pressure activated actions. Thefirst of these actions is a flexing roof action in which the flexibleroof of the closed front end 30 of the stopper 12 flexes inward andexpands sideways in a radial direction as shown by arrows A₁. Thisaction is further illustrated schematically in FIG. 7. As can be seen inFIG. 7, the flexible roof of the closed front end 30 of the stopper 12is shown as a solid line before the pressure within the syringe barrel16 is increased due to an injection. Once an injection is started, thepressure increase within the barrel causes the flexible roof of theclosed front end 30 of the stopper 12 to flex inwardly and expandsideways in a radial direction as shown by the dashed line. Theextension portions 58 limit this flexing such that the flexible roofdoes not invert during an injection.

A second action can be considered a flexing skirt action in which thefirst perimetrical skirt 36 extending around the main body portion 24 ofthe stopper 12 bends toward the inner wall 38 of the syringe barrel 16as shown by arrows A₂.

Finally, a sliding action is provided in which the engagement betweenthe tapered ring 56 of the plunger rod 14 and the notch 44 of the mainbody portion 24 of the stopper 12 forces the main body portion 24 toexpand in the radial direction toward the inner wall 38 of the syringebarrel 16 as shown by arrows A₃. More specifically, the engagementbetween the upwardly angled portion 46 of the notch 44 and an upper edgeof the tapered ring 56 ensures that the stopper 12 is forced in a radialdirection (i.e., toward the inner wall 38) during an injection, therebycontributing to a stronger sealing between the stopper 12 and thesyringe barrel 16. In addition, the engagement between the downwardlyangled portion 48 of the notch 44 and a lower edge of the tapered ring56 ensures that the stopper 12 is forced in a radial direction (i.e.,toward the inner wall 38) during an aspiration, thereby contributing toa stronger sealing between the stopper 12 and the syringe barrel 16.

These active sealing functions allow for low contact pressure betweenthe stopper 12 and the inner walls 38 of the syringe barrel 16, therebyeliminating barrel creep and localized bulging issues when the walls ofthe syringe barrel 16 are thin. The interface between the stopper 12 andthe inner walls 38 of the syringe barrel 16 at assembly is between about0.01 mm/per diameter and 2 mm/per diameter, and desirably, about 0.3mm/per diameter and 0.8 mm/per diameter.

With reference to FIGS. 8-10, a second embodiment of a stopper inaccordance with the present invention, generally denoted as referencenumeral 112, is illustrated. The stopper 112 includes a main bodyportion 124 defining an open rearward end 126 configured to receive theplunger rod 14 and a closed front end 128 that forms a flexible roof.The closed front end 128 of the main body portion 124 includes a firstangled portion 130 and a second angled portion 132, which are both partof the same conical surface that extends to a tip 134. The tip 134includes an extended portion 135 configured to fit inside a tip of thesyringe barrel 16 to minimize the space in the syringe barrel 16 whereunused medication remains after an injection has been completed. Theextended portion 135 may also be used during the assembly of the syringe10 to aid in properly orienting the stopper 112 within the syringebarrel 16.

A first perimetrical skirt 136 is provided that extends around an outercircumference of the main body portion 124 toward the closed front end128. The primary purpose of the first perimetrical skirt 136 is toprovide an “active seal” between the stopper body and an inner wall 38of the syringe barrel 16 as discussed hereinabove. The stopper 112 alsoincludes a second perimetrical skirt 140 extending around an outercircumference of the main body portion 124 toward the open rearward end126. The primary purpose of the second perimetrical skirt 140 is toprovide stability to the stopper 112 in an axial direction and toprevent tilting of the stopper 112. In addition, when fluid pressure isdecreased inside the syringe barrel 116 during an aspiration, the secondperimetrical skirt 140 is forced against the inner wall 38 of thesyringe barrel 16, thereby providing a sealing pressure between thestopper 112 and the inner wall 38 of the syringe barrel 16.

As shown in FIG. 9, the main body portion 124 of the stopper 112 issubstantially hollow and designed to receive an attachment portion 42 ofthe plunger rod 14. A notch 144 is provided that extends around an innercircumference of the main body portion 124. The notch 144 includes anupwardly angled portion 146 and a downwardly angled portion 148, therebyproviding the notch 144 with a conical cross-sectional shape. However,the shape of notch 144 is not to be construed as limiting the presentinvention as other interfaces between the notch 144 and the attachmentportion 42 of the plunger rod 14, such as linear or curved interfaces,could be utilized to provide the same function.

The notch 144 is configured to engage with the attachment portion 42 ofthe plunger rod such that during an injection, the upwardly angledportion 146 engages the attachment portion 42, thereby forcing the mainbody portion 124 in a radial direction (i.e., toward the barrel wall)such that a stronger seal is created between the main body portion 124and the inner wall 38. During an aspiration, the downwardly angledportion 148 engages the attachment portion 42, thereby forcing the mainbody portion 124 in a radial direction (i.e., toward the barrel wall)such that a stronger seal is created between the main body portion 124and the inner wall 38.

The plunger rod 14 used with the second embodiment of the stopper 112 isthe same as the plunger rod 14 illustrated in FIGS. 5 and 6 anddiscussed hereinabove. In addition, the stopper 112 also includes anactive sealing function such that when fluid pressure inside the syringe10 increases due to injection, sealing pressure between the stopper 112and the syringe barrel 16 also increases due to the three separatepressure activated actions discussed hereinabove with reference to FIG.4A.

With reference to FIGS. 11-13, a third embodiment of the stopper,generally denoted as reference numeral 212, is illustrated. The stopper212 includes a main body portion 224 defining an open rearward end 226configured to receive an alternative embodiment of plunger rod 214 (seeFIGS. 14 and 15) and a closed front end 228 that forms a flexible roof.The closed front end 228 of the main body portion 224 includes a firstangled portion 230 and a second angled portion 232, which are both partof the same conical surface that extends to a tip 234. The tip 234includes an extended portion 235 configured to fit inside a tip of thesyringe barrel 16 to minimize the space in the syringe barrel 16 whereunused medication remains after an injection has been completed. Theextended portion 135 may also be used during the assembly of the syringe10 to aid in properly orienting the stopper 112 within the syringebarrel 16.

A first perimetrical skirt 236 is provided that extends around an outercircumference of the main body portion 224 toward the closed front end228. The primary purpose of the first perimetrical skirt 236 is toprovide an “active seal” between the stopper body and an inner wall 38of the syringe barrel 16 as will be discussed in greater detailhereinafter. The stopper 212 also includes a second perimetrical skirt240 extending around an outer circumference of the main body portion 224toward the open rearward end 226. The primary purpose of the secondperimetrical skirt 240 is to provide stability to the stopper 212 in anaxial direction and to prevent tilting of the stopper 212. In addition,when fluid pressure is decreased inside the syringe barrel 16 during anaspiration, the second perimetrical skirt 240 is forced against theinner wall 38 of the syringe barrel 16, thereby providing a sealingpressure between the stopper 212 and the inner wall 38 of the syringebarrel 16.

As shown in FIG. 12, the main body portion 224 of the stopper 212 issubstantially hollow and designed to receive an attachment portion 242of plunger rod 214. A notch 244 is provided that extends around an innercircumference of the main body portion 224. The notch 244 includes anupwardly angled portion 246.

The notch 244 is configured to engage with the attachment portion 242 ofthe plunger rod such that during an injection, the upwardly angledportion 246 engages the attachment portion 242, thereby forcing the mainbody portion 224 in a radial direction (i.e., toward the barrel wall)such that a stronger seal is created between the main body portion 224and the inner wall 38.

An extension 266 extending from the tip 234 toward the open rearward end226 is also provided. The extension 266 has a substantially cylindricalhollow body portion 268 having an opening 270 at a bottom portionthereof facing the open rearward end 226 of stopper 212. The opening 270has a diameter that is smaller than the diameter of the body portion268, thereby creating a bearing surface 272 adjacent to the opening 270.

With reference to FIGS. 14 and 15, the plunger rod 214 may include asyringe plunger body 250 having a front end 252 and a back end 254extending along a longitudinal axis X. The attachment portion 242 isassociated with the front end 252 of the syringe plunger body 250. Theattachment portion 242 includes a tapered ring 256 designed to engagethe notch 244 of the stopper 212 and an extension portion 258 configuredto contact a lower surface 260 of the flexible roof of the closed frontend 228 during an injection, thereby limiting the expansion of theflexible roof in the radial direction. The attachment portion 242 alsoincludes a rod 263 having a conical head 264 extending from the frontend 252 of the syringe plunger body 250 and configured to engage theextension 266 of the stopper 212 as discussed hereinafter.

The syringe plunger body 250 may also include a retaining ring 262positioned adjacent to the open rearward end 226 of the main bodyportion 224 of the stopper 212. The retaining ring 262 is provided toprevent the plunger rod 214 from being removed from the syringe barrel16. With reference to FIG. 13, when the plunger rod 214 is inserted intothe stopper 212 through the open rearward end 226, the tapered ring 256engages the notch 244 and the rod 263 is inserted into the opening 270of the extension 266 such that the plunger rod 214 is locked in placeand is prevented from separating from the stopper 212.

With continued reference to FIG. 13, the rigid plastic stopper 212includes an active sealing function such that when fluid pressure insidethe syringe 10 increases due to injection, sealing pressure between thestopper 212 and the syringe barrel 16 also increases due to threeseparate pressure activated actions as described in detail hereinabovewith reference to the first and second embodiments. During anaspiration, the conical head 264 of the rod 263 contacts the bearingsurface 272 of the extension 266 causing the flexible roof of the mainbody portion 224 to expand in the radial direction toward the inner wall38 of the syringe barrel 216 as a result of the negative pressurepulling the flexible roof up. Such a configuration is suitable forlarger syringe sizes (10 ml-60 ml) where a larger roof area is exposedto negative pressure.

With reference to FIGS. 16-18, a fourth embodiment of the stopper,generally denoted as reference numeral 312, is illustrated. The stopper312 includes a main body portion 324 defining an open rearward end 326configured to receive an alternative embodiment of plunger rod 314 (seeFIGS. 19 and 20) and a closed front end 328 that forms a flexible roof.The closed front end 328 of the main body portion 324 includes a firstangled portion 330 and a second angled portion 332, which are both partof the same conical surface that extends to a tip 334. The tip 334includes an extended portion 335 configured to fit inside a tip of thesyringe barrel 16 to minimize the space in the syringe barrel 16 whereunused medication remains after an injection has been completed. Theextended portion 335 may also be used during the assembly of the syringe10 to aid in properly orienting the stopper 312 within the syringebarrel 16.

A first perimetrical skirt 336 is provided that extends around an outercircumference of the main body portion 324 toward the closed front end328. The primary purpose of the first perimetrical skirt 336 is toprovide an “active seal” between the stopper body and an inner wall 38of the syringe barrel 16 as will be discussed in greater detailhereinafter. The stopper 312 also includes a second perimetrical skirt340 extending around an outer circumference of the main body portion 324toward the open rearward end 326. The primary purpose of the secondperimetrical skirt 340 is to provide stability to the stopper 312 in anaxial direction and to prevent tilting of the stopper 312. In addition,when fluid pressure is decreased inside the syringe barrel 16 during anaspiration, the second perimetrical skirt 340 is forced against theinner wall 38 of the syringe barrel 16, thereby providing a sealingpressure between the stopper 312 and the inner wall 38 of the syringebarrel 16.

As shown in FIG. 17, the main body portion 324 of the stopper 312 issubstantially hollow and designed to receive an attachment portion 342of plunger rod 314. A notch 344 is provided that extends around an innercircumference of the main body portion 324. The notch 344 includes anupwardly angled portion 346. A groove 345 may be provided along an edgeof the flexible roof of the main body portion 324 to tune the stiffnessof the flexible roof and/or the main body portion 324 in order toachieve a desired flexing response.

The notch 344 is configured to engage with the attachment portion 342 ofthe plunger rod such that during an injection, the upwardly angledportion 346 engages the attachment portion 342, thereby forcing the mainbody portion 324 in a radial direction (i.e., toward the barrel wall)such that a stronger seal is created between the main body portion 324and the inner wall 38.

An extension 366 extending from the tip 334 toward the open rearward end326 is also provided. The extension 366 has a substantially cylindricalhollow body portion 368 having bearing surface 372 extending from andaround an outer diameter thereof.

With reference to FIGS. 19 and 20, the plunger rod 314 includes asyringe plunger body 350 having a front end 352 and a back end 354extending along a longitudinal axis X. The attachment portion 342 isassociated with the front end 352 of the syringe plunger body 350. Theattachment portion 342 includes a tapered ring 356 designed to engagethe notch 244 of the stopper 312 and a cylindrical body 361 having anopening 363 extending from the front end 352 of the syringe plunger body350 and configured to engage the extension 366 of the stopper 312 asdiscussed hereinafter. The opening 363 has a diameter that is smallerthan the diameter of the body 361, thereby creating a bearing surface364 adjacent to the opening 363.

The syringe plunger body 350 may also include a retaining ring 362positioned adjacent to the open rearward end 326 of the main bodyportion 324 of the stopper 312. The retaining ring 362 is provided toprevent the plunger rod 314 from being removed from the syringe barrel16. With reference to FIG. 18, when the plunger rod 314 is inserted intothe stopper 312 through the open rearward end 326, the tapered ring 356engages the notch 344 and the extension 366 is inserted into the opening363 of the cylindrical body 361 such that the plunger rod 314 is lockedin place and is prevented from separating from the stopper 312.

With continued reference to FIG. 18, the rigid plastic stopper 312includes an active sealing function such that when fluid pressure insidethe syringe 10 increases due to injection, sealing pressure between thestopper 312 and the syringe barrel 16 also increases due to threeseparate pressure activated actions as described in detail hereinabovewith reference to the first through third embodiments. During anaspiration, the bearing surface 364 of the cylindrical body 361 contactsthe bearing surface 372 of the extension 366 causing the flexible roofof the main body portion 324 to expand in the radial direction towardthe inner wall 38 of the syringe barrel 216 as a result of the negativepressure pulling the flexible roof up. Such a configuration is alsosuitable for larger syringe sizes (10 ml-60 ml) where a larger roof areais exposed to negative pressure.

With reference to FIGS. 21-23, a fifth embodiment of the stopper,generally denoted as reference numeral 412, is illustrated. The stopper412 includes a main body portion 424 defining an open rearward end 426configured to receive the plunger rod 414 (see FIGS. 24 and 25) and aclosed front end 428 that forms a flexible roof. The closed front end428 of the main body portion 424 includes a first angled portion 430 anda second angled portion 432, which are both part of the same conicalsurface that extends to a tip 434, thereby providing the closed frontend 428 with a substantially conical appearance.

A first perimetrical skirt 436 is provided that extends around an outercircumference of the main body portion 424 toward the closed front end428. The primary purpose of the first perimetrical skirt 436 is toprovide an “active seal” between the stopper body and an inner wall 38of the syringe barrel 16 as discussed hereinabove. The stopper 412 alsoincludes a second perimetrical skirt 440 extending around an outercircumference of the main body portion 424 toward the open rearward end426. The primary purpose of the second perimetrical skirt 440 is toprovide stability to the stopper 412 in an axial direction and toprevent tilting of the stopper 412.

In addition, when fluid pressure is decreased inside the syringe barrel416 during an aspiration, the second perimetrical skirt 440 is forcedagainst the inner wall 38 of the syringe barrel 16, thereby providing asealing pressure between the stopper 412 and the inner wall 38 of thesyringe barrel 16.

As shown in FIG. 23, the main body portion 424 of the stopper 412 issubstantially hollow and designed to receive an attachment portion 442of plunger rod 414. A flange 444 extends toward the center of stopper412 and around an inner circumference of the main body portion 424. Theflange 444 includes an upwardly angled portion 446 and a downwardlyangled portion 448.

The flange 444 is configured to engage with the attachment portion 442of the plunger rod 414 such that during an aspiration, the downwardlyangled portion 448 engages the attachment portion 442, thereby forcingthe main body portion 424 in a radial direction (i.e., toward barrelwall) such that a stronger seal is created between the main body portion424 and the inner wall 38.

With reference to FIGS. 24 and 25, the plunger rod 414 may include asyringe plunger body 450 having a front end 452 and a back end 454extending along a longitudinal axis X. The attachment portion 442 isassociated with the front end 452 of the syringe plunger body 450. Theattachment portion 442 includes a first ring 456 designed to engage theflange 444 of the stopper 412 and an extension portion 458 configured tocontact a lower surface 460 of the flexible roof of the closed front end428 during an injection, thereby limiting the expansion of the flexibleroof in the radial direction. The attachment portion 442 also includes asecond ring 461 provided at the front end 452. The second ring 461 isconfigured such that, during an injection, an upper surface of thesecond ring 461 engages the lower surface 460 of the flexible roof,thereby forcing the main body portion 424 in a radial direction (i.e.,toward the barrel wall) such that a stronger seal is created between themain body portion 424 and the inner wall 38.

The syringe plunger body 450 may also include a retaining ring 462positioned adjacent to the open rearward end 426 of the main bodyportion 424 of the stopper 412. The retaining ring 462 is provided toprevent the plunger rod 414 from being removed from the syringe barrel16. With reference to FIG. 23, when the plunger rod 414 is inserted intothe stopper 412 through the open rearward end 426, the first ring 456engages the flange 444 such that the plunger rod 414 is locked in placeand is prevented from separating from the stopper 412.

With reference to FIGS. 26-28, a sixth embodiment of the stopper,generally denoted as reference numeral 512, is illustrated. The stopper512 includes a main body portion 524 defining an open rearward end 526configured to receive the plunger rod 514 (see FIGS. 29 and 30) and aclosed front end 528 that forms a flexible roof. The closed front end528 of the main body portion 524 includes a first angled portion 530 anda second angled portion 532, which are both part of the same conicalsurface that extends to a tip 534, thereby providing the closed frontend 528 with a substantially conical appearance.

A first perimetrical skirt 536 is provided that extends around an outercircumference of the main body portion 524 toward the closed front end528. The primary purpose of the first perimetrical skirt 536 is toprovide an “active seal” between the stopper body and an inner wall 38of the syringe barrel 16 as discussed hereinabove. The stopper 512 alsoincludes a second perimetrical skirt 540 extending around an outercircumference of the main body portion 524 toward the open rearward end526. The primary purpose of the second perimetrical skirt 540 is toprovide stability to the stopper 512 in an axial direction and toprevent tilting of the stopper 512. In addition, when fluid pressure isdecreased inside the syringe barrel 16 during an aspiration, the secondperimetrical skirt 540 is forced against the inner wall 38 of thesyringe barrel 16, thereby providing a sealing pressure between thestopper 512 and the inner wall 38 of the syringe barrel 16.

As shown in FIG. 27, the main body portion 524 of the stopper 512 issubstantially hollow and designed to receive an attachment portion 542of plunger rod 514. A flange 544 extends toward the center of stopper512 and around an inner circumference of the main body portion 524. Theflange 544 includes an upwardly angled portion 546 and a downwardlyangled portion 548.

The flange 544 is configured to engage with the attachment portion 542of the plunger rod 514 such that during an aspiration, the downwardlyangled portion 548 engages the attachment portion 542, thereby forcingthe main body portion 524 in a radial direction (i.e., toward barrelwall) such that a stronger seal is created between the main body portion524 and the inner wall 38.

With reference to FIGS. 29 and 30, the plunger rod 514 may include an asyringe plunger body 550 having a front end 552 and a back end 554extending along a longitudinal axis X. The attachment portion 542 isassociated with the front end 552 of the syringe plunger body 550. Theattachment portion 542 includes a disk 556 designed to engage the flange544 of the stopper 512. The disk 556 also includes a tapered surface 561provided at the front end 552. The tapered surface 561 is configuredsuch that during an injection, it engages the lower surface 560 of theflexible roof, thereby forcing the main body portion 524 in a radialdirection (i.e., toward the barrel wall) such that a stronger seal iscreated between the main body portion 524 and the inner wall 38.

The syringe plunger body 550 may also include a retaining ring 562positioned adjacent to the open rearward end 526 of the main bodyportion 524 of the stopper 512. The retaining ring 562 is provided toprevent the plunger rod 514 from being removed from the syringe barrel16. With reference to FIG. 28, when the plunger rod 514 is inserted intothe stopper 512 through the open rearward end 526, the disk 556 engagesthe flange 544 such that the plunger rod 514 is locked in place and isprevented from separating from the stopper 512.

With reference to FIGS. 31 and 32, the syringe barrel 16 may include anarea 100 near the fluid dispensing end thereof having an inner diameterD₁ that is greater than an inner diameter D₂ of remaining areas of thesyringe barrel 16. This area is configured to receive the firstperimetrical skirt 436 when the first perimetrical skirt 436 ispositioned adjacent thereto, such as during storage. During storage,polymer creep phenomena (i.e., permanent deformation/relaxation) occurson the outer diameter of first perimetrical skirt 436 due to the initialinterference and contact stress between the stopper 412 and barrel 16.By providing such an area 100, it can be ensured that the firstperimetrical skirt 436 will creep/adjust into the area 100, which has adiameter D₁ that is larger than the diameter D₂ of the rest of thebarrel 16, thereby ensuring intimate contact between the inner wall 38of the barrel 16 and the stopper 412 when the syringe 10 is used. Thearea 100 may have a depth of about 0.01 mm to about 0.4 mm and desirablya depth of about 0.1 mm to about 0.3 mm.

While this feature of the present invention was discussed in relation tothe fifth embodiment, any of the above-described embodiments may includea syringe barrel 16 having such an area 100. Furthermore, if area 100 isnot provided, the same stopper design could be made to work by carefullydesigning the stopper material to undergo only controlled amount ofcreep (i.e., controlled creep) during the shelf life of the syringe orduring its sterilization. In addition, stopper 412 may further include anotch 462 positioned in the lower surface 460 of the flexible roofbeneath the tip 434 to tune the stiffness of the flexible roof and/orthe main body portion 424 in order to achieve a desired flexingresponse.

While specific embodiments of the invention have been described indetail, it will be appreciated by those skilled in the art that variousmodifications and alternatives to those details could be developed inlight of the overall teachings of the disclosure. Accordingly, theparticular arrangements disclosed are meant to be illustrative only andnot limiting as to the scope of invention which is to be given the fullbreadth of the claims appended and any and all equivalents thereof.

1. A stopper adapted for attachment with a plunger rod for use within asyringe barrel, the stopper comprising: a main body portion defining anopen rearward end configured to receive the plunger rod, an engagementportion provided along an inner circumference of the main body portionconfigured to engage at least a top portion of the plunger rod, and aclosed front end forming a flexible roof; and a first perimetrical skirtextending around an outer circumference of the main body portion towardthe closed front end of the main body portion, wherein, when fluidpressure is increased inside the syringe barrel during an injection, theflexible roof expands in a radial direction toward an inner wall of thesyringe barrel, the first perimetrical skirt is forced against the innerwall of the syringe barrel, and an engagement between the plunger rodand the engagement portion forces the main body portion to expand in theradial direction toward the inner wall of the syringe barrel, therebyproviding a sealing pressure between the stopper and the inner wall ofthe syringe barrel.
 2. The stopper of claim 1, wherein the closed frontend of the main body has a conical shape with a tip.
 3. The stopper ofclaim 2, wherein the tip comprises an extended portion configured to fitinside a tip of the syringe barrel.
 4. The stopper of claim 2, furthercomprising an extension extending from the tip toward the open rearwardend, the extension configured to be connected to the plunger rod tocause the flexible roof to expand in the radial direction toward theinner wall of the syringe barrel during an aspiration.
 5. The stopper ofclaim 1, wherein the stopper, the plunger rod, and the syringe barrelare manufactured from the same material.
 6. The stopper of claim 1,wherein the stopper is manufactured from a rigid or semi-rigid polymericmaterial.
 7. The stopper of claim 6, wherein the rigid or semi-rigidpolymeric material has an elastic modulus in the range of about 0.01 GPato about 5 GPa.
 8. The stopper of claim 7, wherein the rigid orsemi-rigid polymeric material has an elastic modulus in the range ofabout 0.6 GPa to about 2 GPa.
 9. The stopper of claim 7, wherein therigid or semi-rigid polymeric material is selected from the groupconsisting of: polyolefines, polyamides, polyesters, polystyrene,polyurethane, polycarbonate, acrylonitrile-butadiene-styrene,fluoropolymers, ionomers, polyacrylates, or any combination thereof. 10.The stopper of claim 1, wherein the flexible roof has a thickness ofabout 0.1 mm to about 3 mm.
 11. The stopper of claim 10, wherein theflexible roof has a thickness of about 0.3 mm to about 1.2 mm.
 12. Thestopper of claim 1, wherein the first perimetrical skirt has a thicknessof about 0.05 mm to about 3 mm and a length of about 1 mm to about 10mm.
 13. The stopper of claim 12, wherein the first perimetrical skirthas a thickness of about 0.2 mm to about 0.5 mm.
 14. The stopper ofclaim 1, further comprising: a second perimetrical skirt extendingaround an outer circumference of the main body portion toward the openrearward end of the main body such that the second perimetrical skirtprovides stability to the stopper in an axial direction, wherein, whenfluid pressure is decreased inside the syringe barrel during anaspiration, the second perimetrical skirt is forced against the innerwall of the syringe barrel, thereby providing a sealing pressure betweenthe stopper and the inner wall of the syringe barrel.
 15. The stopper ofclaim 14, wherein the second perimetrical skirt has a thickness of about0.05 mm to about 3 mm and a length of about 1 mm to about 10 mm.
 16. Thestopper of claim 15, wherein the second perimetrical skirt has athickness of about 0.2 mm to about 0.5 mm.
 17. The stopper of claim 1,wherein the engagement portion comprises a notch.
 18. The stopper ofclaim 17, wherein the top portion of the plunger rod includes a taperedring that engages the notch of the main body such that the engagementbetween the plunger rod and the notch forces the main body portion toexpand in the radial direction toward the inner wall of the syringebarrel during both an injection and an aspiration.
 19. The stopper ofclaim 18, wherein the notch comprises an upwardly angled portion and adownwardly angled portion.
 20. The stopper of claim 19, wherein theupwardly angled portion has an angle of about 10° to about 80° asmeasured from a vertical line extending between the upwardly angledportion and the downwardly angled portion.
 21. The stopper of claim 20,wherein the upwardly angled portion has an angle of about 25° to about55° as measured from a vertical line extending between the upwardlyangled portion and the downwardly angled portion.
 22. The stopper ofclaim 19, wherein the downwardly angled portion has an angle of about10° to about 80° as measured from a vertical line extending between theupwardly angled portion and the downwardly angled portion.
 23. Thestopper of claim 22, wherein the downwardly angled portion has an angleof about 25° to about 55° as measured from a vertical line extendingbetween the upwardly angled portion and the downwardly angled portion.24. The stopper of claim 1, wherein the engagement portion comprises aprotruding portion.
 25. The stopper of claim 24, wherein the top portionof the plunger rod includes a notch formed around an outer circumferencethereof that engages the protruding portion of the main body such thatthe engagement between the plunger rod and the protruding portion forcesthe main body portion to expand in the radial direction toward the innerwall of the syringe barrel during both an injection and an aspiration.26. A syringe comprising: a) a substantially cylindrical syringe barrelcomprising a fluid dispensing end and an open end; b) a stopperconfigured to be received within the open end of the syringe barrel, thestopper comprising: i) a main body portion defining an open rearward endconfigured to receive the plunger rod, an engagement portion providedalong an inner circumference of the main body portion, and a closedfront end forming a flexible root and ii) a first perimetrical skirtextending around an outer circumference of the main body portion towardthe closed front end of the main body portion; and c) a plunger rodhaving a plunger rod body extending along a longitudinal axis, theplunger rod body comprising a front attachment end configured to engagethe engagement portion provided along the inner circumference of themain body portion of the stopper and a back end, wherein, when fluidpressure is increased inside the syringe barrel during an injection, theflexible roof expands in a radial direction toward an inner wall of thesyringe barrel, the first perimetrical skirt is forced against the innerwall of the syringe barrel, and an engagement between the plunger rodand the engagement portion forces the main body portion to expand in theradial direction toward the inner wall of the syringe barrel, therebyproviding a sealing pressure between the stopper and the inner wall ofthe syringe barrel.
 27. The syringe of claim 26, wherein the frontattachment end of the syringe plunger body comprises an extensionportion configured to contact a lower surface of the flexible roofduring an injection, thereby limiting the expansion of the flexible roofin the radial direction.
 28. A plunger rod and stopper assembly adaptedfor use with a syringe barrel, the assembly comprising: a) a stoppercomprising: i) a main body portion defining an open rearward endconfigured to receive the plunger rod, an engagement portion providedalong an inner circumference of the main body portion, and a closedfront end forming a flexible roof; and ii) a first perimetrical skirtextending around an outer circumference of the main body portion towardthe closed front end of the main body; and b) a plunger rod having aplunger rod body extending along a longitudinal axis, the plunger rodbody comprising a front attachment end configured to engage theengagement portion provided along the inner circumference of the mainbody portion of the stopper and a back end, wherein, when fluid pressureis increased inside the syringe barrel during an injection, the flexibleroof expands in a radial direction toward an inner wall of the syringebarrel, the first perimetrical skirt is forced against the inner wall ofthe syringe barrel, and an engagement between the plunger rod and theengagement portion forces the main body portion to expand in the radialdirection toward the inner wall of the syringe barrel, thereby providinga sealing pressure between the stopper and the inner wall of the syringebarrel.
 29. The assembly of claim 28, wherein the front attachment endof the syringe plunger body comprises an extension portion configured tocontact a lower surface of the flexible roof during an injection,thereby limiting the expansion of the flexible roof in the radialdirection.